AU2015344911A1

AU2015344911A1 - Electromagnetic actuator with multiple windings

Info

Publication number: AU2015344911A1
Application number: AU2015344911A
Authority: AU
Inventors: Alexandre CHAMAGNE
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2014-11-14
Filing date: 2015-11-10
Publication date: 2017-06-01
Anticipated expiration: 2035-11-10
Also published as: AU2015344911B2; WO2016075404A1; FR3028663A1; CN107148660B; CN107148660A; EP3218917B1; FR3028663B1; EP3218917A1

Abstract

A line protection electromagnetic actuator, comprising a differential winding (2) generating a magnetic field in response to a differential fault on the current line to be protected, and a magnetic winding (1). This electromagnetic actuator is characterised in that it also comprises a third winding (3) engaged with said differential winding (2) and magnetic winding (1), traversed by a current of which the direction is reversed relative to that of the differential winding (2) when a current flows between the phase Ph and the neutral N of the actuator, and generating a magnetic field opposed to the magnetic field created by the differential winding (2), said third winding (3) being connected in parallel to the differential winding (2), between the phase Ph and the neutral N of the line to be protected, and controlled by control means.

Description

1 PCT/FR2015/053040

ELECTROMAGNETIC ACTUATOR WITH MULTIPLE WINDINGS 5 FIELD OF THE INVENTION

The present invention relates to an electromagnetic actuator whose immunity to electric shocks has been enhanced. It relates in particular to electromechanical actuators which are used in conjunction with triggering locks of electric line protection devices, for example differential and / or voltage dependent disjunction devices. 10

These devices must trigger under very specific conditions, typically when an imbalance occurs between the sum of the incoming currents and the sum of the outgoing currents of the line protected by the device in question, which corresponds to a "differential" protection due to a differential fault, or when the current is abnormally is high, which corresponds to a "magnetic" protection following a short circuit fault.

An actuator conventionally comprises coils surrounding a movable magnetic core capable of moving from a rest position to an actuating position under the effect of the magnetic field created by the coils. More specifically, it comprises: 20 A coil said to be "differential" generating a magnetic field in response to a differential type fault on the current line to be protected; A coil said to be "magnetic" generating a magnetic field in response to a short-25 circuit type fault on the current line to be protected.

It is in fact a multi-winding actuator which consists of a compact solution making it possible to provide different types of protection with the same actuator.

so BACKGROUND OF THE INVENTION

The problem which this invention proposes to solve is as follows: the circuits protected by electrical devices such as those mentioned above undergo tests and are subjected to electromagnetic compatibility (EMC) tests in order to check whether they are 2 sufficiently immune to disturbances from other equipment, or more generally from the environment.

These tests are standardized, and consist in sending several waves of current 8/20ps, 5 then a voltage wave 1.2/50ps in the electrical device. The device must not trip under these conditions. This means that by applying the above mentioned surges there must be no dielectric breakdown or damage to the component inside the device.

It is customary for such an actuator to be piloted by a control element, for example a io thyristor, which is itself activated when the detection circuit of the device detects a fault. A varistor protects the control element in case of an overvoltage surge such as a 1.2/50ps voltage surge. This varistor, placed downstream of the differential coil, becomes conductive beyond a defined voltage threshold and thus makes it possible to limit the voltage at the terminals of the control element to a value lower than the is breakdown voltage of the control element.

When a 1,2/50ps voltage wave circulates in the differential coil, it can cause the device to unwantedly trip at 2kV, whereas the standard requires that the actuator be able to withstand shocks without triggering below 2kV. 20

When an 8/20ps current surge flows in the magnetic coil, and if the windings of the differential coil are imbricated with the windings of the magnetic coil, by electromagnetic coupling, a significant voltage is induced across the terminals of differential coil which causes dielectric breakdowns with destruction of the differential 25 protection.

To overcome these two problems, the solution at present consists of placing an additional varistor at the terminals of the differential coil. This solution makes it possible to avoid 8/20ps current surge breakdowns, but has the disadvantage of 3o increasing the voltage (of the order of 1000V) across the terminals of the control element during a voltage surge 1,2/50ps because of the very strong current (of the order of 1000A) drained by the two varistors in series. The control element, so as not to degrade prematurely, must therefore be able to withstand such load. It will thus 3 consist, for example, of a thyristor 1200V or an IGBT, that is to say a relatively expensive component.

It is possible to add a resistor upstream of the differential coil in order to limit the current 5 which passes through the varistors, but this calls into question the compactness of the actuator and the control element will still be chosen from expensive components to support both the 1,2/50ps voltage waves and the 8/20ps current waves.

The current solution is therefore relatively expensive. 10

SUMMARY OF THE INVENTION

The objective pursued in the context of the present invention therefore consists in developing an electromagnetic actuator capable of withstanding shocks caused by short over-voltages not caused by a malfunction of the circuit itself, without inducing a is triggering of the device in which the actuator is integrated, nor deterioration of components. The manufacture of such an electromagnetic actuator must also be simple to implement and inexpensive.

To meet this objective, the electromagnetic actuator according to the invention 2o comprises, conventionally: * A differential coil generating a magnetic field in response to a differential type fault on the line of current to be protected; 25 A magnetic coil imbricated with the differential coil and generating a magnetic field in response to a short circuit fault on the current line to be protected.

The main characteristic of this actuator is that it also comprises a third coil imbricated with said differential and magnetic coils, traversed by a current whose direction is reversed with respect to that of the differential coil when a current flows between the 3o phase and the neutral of the actuator and generating a magnetic field opposite to the magnetic field created by the differential coil, the said third coil being connected in parallel with the differential coil between phase Ph and neutral N of the line to be protected and piloted by control method. 4

According to the invention, said control method consists of a varistor-type voltage threshold-controlled component added in series downstream of the third coil between the phase Ph and the neutral N of the line to be protected. This component makes it possible to authorise or not the third coil to be traversed by current as a function of a 5 voltage threshold depending on the component itself. Without the existence of such a component, the third coil would be continuously traversed by current, and would either end up overheating/failing or would continuously trip.

Thus, during a voltage wave 1,2/50ps, the two varistors (that downstream of the io differential coil and that downstream of the third coil) become simultaneously activated since the voltage threshold is exceeded and the differential coil as well as the third coil are then traversed by current. The current flowing in the third coil creates a magnetic field which is opposed to that created by the differential coil, which makes it possible to inhibit the magnetic force exerted on the moveable magnetic core of the is electromagnetic actuator.

This is possible, for example, if the direction of winding of the third coil is reversed with respect to the direction of winding of the differential coil. There are, however, other means for reversing the direction of a current, with the two coils in question wound in 2o the same direction. In this case, it is sufficient, for example, to turn one coil relative to the other, in this case to turn the third coil with respect to the differential coil. In other words, the beginning extremity of the third con is found in the vicinity of the end of the differential coil. 25 This configuration makes it possible to suppress unwanted trips and hardware degradations connected to 1,2/50ps surges, this up to 4000V.

Otherwise, when the magnetic coil is traversed by a current surge 8/20ps, it generates a magnetic field. The third coil picks up this magnetic field by virtue of its positioning 3o in the vicinity of the magnetic coil, and creates naturally, by magnetic coupling, an induced current which passes through it in the opposite direction to the current flowing in the magnetic coil. 5

This induced current then creates a magnetic field which is opposed to that created by the magnetic coil. The resulting magnetic field is significantly less than that initially created by the magnetic coil, which makes it possible to reduce the induced voltage on the differential coil. 5

This configuration avoids the breakdown caused by current surges 8/20ps.

Since the induced voltage on the differential coil is reduced, the downstream components, i.e. the varistor at the terminals of the control element and the control 10 element, can be selected in a lower range and hence less expensive.

The invention is therefore partly based on the fact that the three coils are located in the same defined space in order to have a magnetic coupling between them. The three coils can even be coaxial in order to simplify their winding and positioning within the is actuator. This configuration ensures maximum compactness of the actuator.

The invention is therefore partly based on the fact that the three coils are located in the same defined space in order to have a magnetic coupling between them. The three coils can even be coaxial in order to simplify their winding and positioning within the 2o actuator. This configuration ensures maximum compactness of the actuator.

The invention also protects an electrical line protection device comprising an electromagnetic actuator as described above. 25 The present invention will be better understood from the following detailed description and the accompanying drawings, which are provided by way of illustration only, without limiting the present invention.

BRIEF DESCRIPTION OF THE FIGURES 3o The invention will now be described in more detail with reference to the accompanying drawings, in which:

Figure 1 represents an electrical diagram of the actuator according to a first configuration of the invention; 6

Figure 2 illustrates an electric actuator diagram according to a second configuration of the invention. 5 The actuator of the invention as illustrated in Figures 1 and 2 comprises a magnetic coil (1) and a differential coil (2) connected in parallel to the protected line, that is to say typically between phase Ph and Neutral N. This actuator is placed conventionally upstream of a load present on the line to be protected. io These coils (1,2) surround a movable magnetic core (not shown) capable of moving from a rest position to an actuating position under the effect of the magnetic field created by the coils (1, 2) so as to close or open the contacts (7) positioned upstream of the load. is This actuator is piloted by a control element (5), a thyristor in this case, itself activated when the detection circuit (not shown) of the device detects a fault. This thyristor (5) is placed downstream of the differential coil (2) between the phase Ph and the neutral N. 2o A varistor (4), connected in parallel to the thyristor (5), protects the latter in the event of an overvoltage surge.

With reference to Figure 1, this actuator also comprises a third coil (3), the winding direction of which is reversed with respect to that of the differential coil (2), as 25 illustrated by the two arrows.

Referring to Figure 2, this actuator further comprises a third coil (3) having a winding direction identical to that of the differential coil (2), but which is positioned upside down with respect to the differential coil (2). In other words, these two coils (3, 2) are inverted 3o relative to one another. Hence, the starting extremity (11) of the third coil (3) is thus located in the vicinity of the end extremity (10) of the differential coil (2), and the end extremity (9) of the third coil (3) is located in the vicinity of the start extremity (8) of the differential coil (2). 7

The three coils (1, 2, 3) are separated from one another in Figure 1 for the sake of clarity, but are in fact imbricated with one another so as to generate a magnetic coupling. 5 By this magnetic coupling, coil (3) will always generate a magnetic field opposite to the field generated by the magnetic coil (1), in particular during a current surge 8/20ps. Consequently, the voltage at the terminals of the differential coil (2) is reduced, thereby avoiding dielectric breakdowns and deterioration of the adjacent varistor and thyristor. io An additional varistor (6) is added downstream of the third coil (3), so that the latter is not continuously powered. In the case of a voltage wave 1,2/50ps, the varistors (4, 6) become simultaneously conductive, and the coils (2, 3) are then traversed by current. The current flowing in the third coil (3) creates a magnetic field which is opposed to that created in the differential coil (2) since the winding directions are inversed. These is two opposite magnetic fields make it possible to inhibit the magnetic force exerted on the moveable core so that the latter does not move under the effect of a voltage surge 1,2/50ps, hence no undesired triggering of the actuator.

In general, it is preferable for the magnetic field generated by the differential coil to be 2o in the same direction as that generated by the magnetic coil. However, the opposite could be possible, conditional on delaying the differential function in order to leave the time required for the magnetic coil to trigger the product since there could be interference between the two coils (magnetic and differential) in case of simultaneous operation. 25

The configurations shown in the aforementioned figures are only some possible, nonlimiting, examples of the invention which, on the contrary, encompasses variants of forms and designs within the scope of those skilled in the art.

Claims

1. An electromagnetic line protection actuator comprising several coils surrounding a movable magnetic core capable of moving from a rest position to an actuating position under the effect of the magnetic field created by the coils and comprising: a differential coil (2) generating a magnetic field in response to a differential type fault on the current line to be protected; a magnetic coil (1) imbricated with the differential coil (2) and generating a magnetic field in response to a short circuit fault on the current line to be protected; characterised in that it also comprises a third coil (3) imbricated with the differential coil (2) and the magnetic coil (1), traversed by a current whose direction is reversed with respect to that of the differential coil (2) when a current flows between phase Ph and neutral N of the actuator, and generating a magnetic field opposite to the magnetic field created by the differential coil (2), the third coil (3) being connected in parallel to the differential coil (2), between the phase Ph and the neutral N of the line to be protected, and controlled by control means.

2. The electromagnetic actuator according to the preceding claim, characterised in that the control means consists of a varistor type voltage threshold controlled component (7), added in series downstream of the third coil (3), between the Phase Ph and the neutral N of the line to be protected.

3. The electromagnetic actuator as claimed in any one of the preceding claims, characterised in that the direction of winding of the third coil (3) is reversed with respect to that of the differential coil (2).

4. The electromagnetic actuator as claimed in any one of claims 1 and 2, characterised in that the winding direction of the third coil (3) is identical to that of the differential coil (2) and in that the third coil (3) is returned with respect to the differential coil (2).

5. The electromagnetic actuator according to any one of the preceding claims, characterised in that the three coils (1,2, 3) are coaxial.

6. An electrical line protection device comprising an electromagnetic actuator as described in the preceding claims.